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st: Looping questions

From   "kelly johnson" <>
Subject   st: Looping questions
Date   Tue, 09 Aug 2005 08:05:18 -0400


I can do all of this interactively, but need help writing loops.

(1) Suppose I have a variable, say Var1

How can I write a fundction that calculates the change between successive observations of 10 elements of this variable? Ie. Assume the data is sorted by date, decending. The first observation is (Var1[_n] -Var1[_n+10])/Var[_n+10], the second observation is (Var1[_n+2]-Var1[_n+11])/Var1[_n+11], and so on...Is this an instance where I can use the -rolling- command? If so, how?

(2) Now suppose I want to do this same calculation across say, a hundred variables Var1-Var100. How can I loop across the variables in an efficiant manner?

(3) A more general type of loop: suppose I have 100 variables, and I want to display the mean and std. Deviation of each varible.

Any help will be greatly appreciated. Please be specific regarding the coding!



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